Start by clarifying the input format and edge cases, then outline a robust parsing strategy that handles malformed lines and whitespace. Emphasize per-transaction rounding before summation and discuss trade-offs between simplicity and correctness.
Pro tip: Mention that you would use a decimal library or integer cents to avoid floating-point errors, and that you'd log or skip malformed lines with a clear error message. This shows attention to production-quality code and financial accuracy.
Ask about the exact CSV format, expected handling of malformed lines (skip vs. error), and whether currency conversion is needed. Confirm rounding rules and zero-amount behavior.
Outline a line-by-line parser that trims whitespace, splits on commas, and validates field count and types. Use a robust CSV parser if available, but be prepared to implement manually.
For each valid transaction, calculate fee = amount * fee_pct / 100, round to two decimal places using a reliable method (e.g., Decimal or integer cents), then accumulate the total.
Decide on error handling: skip malformed lines, log warnings, or throw exceptions. Ensure zero-amount rows contribute zero fee and that extra whitespace is trimmed.
Walk through test cases: valid input, malformed lines, whitespace, zero amounts, and rounding edge cases (e.g., 0.005). Verify the total sum matches expected results.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.